DUESSELDORF, Germany — How could someone once diagnosed with suicidal tendencies get a job as a commercial pilot, entrusted with the lives of hundreds of people? That’s the question being asked after officials confirmed Monday that Germanwings co-pilot Andreas Lubitz received lengthy psychotherapy before receiving his pilot’s license.

All 150 people on board were killed by what prosecutors believe was a deliberate decision by Lubitz to slam the Airbus A320 he was flying from Barcelona to Duesseldorf into a mountain in the French Alps last Tuesday.

Lufthansa, Germanwings’ parent company, declined to say whether it knew of Lubitz’s mental health problems. But it said the young pilot had passed all required medical checks since starting work for its subsidiary two years ago.